Update AF: DECAF (Coffein & AF) / CABG-AF - Dr. Gregory Marcus and Dr. Florian Herrmann

Dear colleagues, in partnership with Theologus at home, we welcome Dr. Gregory Marcus in San Francisco, California, USA, and Dr. Lian in Munich, Germany, for an update on atrial fibrillation with two very important studies published by our two guests very recently: DECAF on coffee consumption in patients with atrial fibrillation, and the Munich study on new-onset atrial fibrillation after coronary artery bypass grafting. Dear Dr. Hammer, we are very happy to host for the first time a heart surgeon at home, and dear Greg, welcome back at Marcus at home after our 2022 webinar on alcohol and coffee intake in atrial fibrillation. Happy to have you back.

Thanks for joining also from my side. As a brief introduction, I think Dr. Marcus doesn't need much of that. He's an endowed professor in atrial fibrillation research, probably the leading working group when it comes to the effects of caffeine and alcohol on atrial fibrillation, and recently published studies on that. That's where we come together here. Also, a study that was presented at the American Heart Association meeting. Professor Marcus is Associate Chief of Cardiology for Research at the University of California, San Francisco Health Institute, and he's Associate Editor at JAMA as well. As I said, his research interest is atrial fibrillation, and he's conducted numerous trials on that. We are very happy to have you here again and hear some of your thoughts on the most recent one, the DECAF study, and also maybe hear your comments which you published as an editorial on the study by Florian Hammond and Dr. Dr. Herman. Thank you for coming. We are very happy to have a heart surgeon in this round for the first time. Dr. Hammerman has quite some research achievement and won prizes and got research funding from the KUNAR Forinius, and recently last year was awarded a PRIME Advanced Clinician Scientist Booster Award to facilitate his research next to his clinical duties. We are very keen to hear your presentation on the CABG-AF study on atrial fibrillation post-bypass surgery. So without further ado, I would ask you, Dr. Marcus, first to start with your presentation. The floor is yours.

Well, maybe give the word to Dr. Herman first if you like. We have some particular questions maybe.

Thanks. I read the publication online and I was impressed. It was a very interesting trial, and that's definitely shown by the amount of views it's already received, almost 150,000 views, which is spectacular. It's very interesting. It's also related to cardiac surgery a little bit because it's the same recommendation that we frequently make as well about caffeine, and I think a study in this area might be interesting as well in the future because there's no actual data that's related to caffeine intake after cardiac surgery. I haven't found any yet. We still make the recommendation that patients shouldn't be drinking caffeinated coffee after surgery. So that's one interesting thought. I saw that looking deeper into your data, I saw that the proportion of patients in each group that had a certain amount of specific medications were very similar. Is that something that you stratified in randomization?

And my second question is about the topic clinically relevant AF because I did a lot of research in this study on subclinical AF, which I didn't expect before, but it developed. The more data came in, you saw it was much more subclinical AF than clinical AF. How would that be something that you're interested in, also with caffeinated drinks?

That's the exact thought I had.

Before we give the word to Dr. Herman for his presentation, one question I have: obviously we have to rely on the statements of the patients concerning their coffee use. I was so impressed in your alcohol study that you provided people with a wrist alcohol measurement tool, which is obviously not available for coffee. Is there any humoral factor that we could measure, any toxicological screening that was not only in your study? I understand.

I would have two final questions, Stefan, if I may. The first surely is this is an international study. So do you have any information whether the caffeine content of the different coffee preparations that people receive in the States versus Australia does differ? Surely because the number of coffees per day is quite low in your study, I guess because people who drink a lot of coffee like me are not really willing to participate in this kind of study. And the second question would be there's quite a lot of people who actually had cardiac devices, so in whom you would have 24-hour or so rhythm controls. So if you compare these two groups of people, truly not randomized, those who just have clinical AF versus those with cardiac devices, do you see any difference here?

Is that the reason why you also included decaf in the substance that's not allowed in that group?

All right. Well, thank you. And speaking of real life medicine, Dr. Herman, if we may ask you also to share your slides and show us some of the real life randomized data that we are very keen on and a terribly interesting study for looking after our surgical patients.

First of all, thanks for inviting me to present our study from Munich. I'm honored to be a guest here, especially together with Dr. Marcus, who's a great researcher in the field of arrhythmias, and also I've seen the kind of people that were invited to your talks, and it's really great. So we performed the CABG-AF study in Munich, investigating long-term continuous monitoring of new onset atrial fibrillation after coronary artery bypass grafting. It's a prospective multicenter study. We're funded by the Clinical and the German Research Foundation. The background is the incidence of new onset atrial fibrillation after CABG is around 30% based on registry studies. There's quite a bit of variability, but in large registry studies it says around 30%. The incidence is mainly based on data from telemetric monitoring and intermittent rhythm monitoring and mainly until hospital discharge. So in most studies, time frames didn't extend far past discharge, sometimes up to 30 days, but not much more than that. The current ESC/EACTS guidelines recommend long-term oral anticoagulation should be considered in patients with new onset AF after cardiac surgery. It's a class 2A recommendation. It's a similar recommendation in America in the ACC guidelines. There are a couple issues in our view with these recommendations. First of all, the words 'long-term oral anticoagulation' and then also the fact that it's cardiac surgery and it's not specific types of cardiac surgery because we know that there are differences between different types of procedures and different cohorts of patients. That's the background. The aim of our study was to determine the incidence and the burden of new onset AF in the first 12 months after CABG. It was an investigator-initiated prospective observational study of AF using continuous monitoring in two cardiac surgery centers. We actually planned more centers, but it's such a difficult methodology that it couldn't be expanded much more than two centers. The inclusion criteria were first time isolated CABG for three vessel disease or left main disease, no history of AF or other arrhythmias, and a preoperative left ventricular ejection fraction over 35%. We excluded concomitant cardiac surgery. We just wanted to look at CABG, and we excluded mechanical circulatory support at weaning from bypass. AF was defined based on the algorithm of the implanted monitor at two minutes of AF. The timeline of the study was practically that monitors were implanted at the end of surgery, monitoring started at the end of surgery, continued for one year for the primary endpoint, and then continues until 3 years after surgery. After the three years or after battery depletion, the insertable cardiac monitor can then be removed. Our cohort ended up being 198 patients, with one patient where data collection couldn't be started because the patient died before the whole monitor was initialized. So at the end, we had 197 patients with monitoring data. 25 patients were female, around 13%. It's similar in most CABG cohorts. It's primarily men, which is a limitation of the study. The mean age was 66, which is a typical age for bypass surgery in most cohorts as well. Diabetes was around 40% of patients. A lot of three vessel disease, 50% around left main disease, and primarily bypass surgery on pump, only around 24% off pump surgery. The results: the primary endpoint was the cumulative incidence of new onset AF, and that's shown on the graph on the left. You see that around 48% of patients developed AF in the first year after surgery. That's 95 of the 198 patients. We had a median episode length of 6 minutes, median time to AF or to first AF episode of 3.3 days, and 63% of the episodes were asymptomatic. 67 were not detected in standard monitoring, and the cumulative incidence of AF detected with standard monitoring was around 34%. Here you see the AF burden within the first 12 months after CABG. You see that it's primarily AF in the first weeks, two weeks after surgery. The median AF burden during the first 12 months was 0.07%, which corresponds to 6 hours and 10 minutes of AF. In 90 of the 95 patients who developed AF, the incident episode occurred within the first month, and 77% of the time an AF occurred within the first 30 days after surgery, which you can see in the inset up here showing that most of the AF is in the first month. Here you see an increased burden that's unexpected after 9 months. That's one patient with persistent AF for a time after surgery. If we look at the AF burden by time frame, we see that in the first seven days after surgery, we have a median AF burden of 3.65%. Days 8 to 30, it's 0.04%. And numerically calculating the AF burden, the median burden is 0% after 31 days. There are patients with AF, but if including all the patients, you calculate a median AF burden of 0%. Of the 90 patients with incident episodes in the first 30 days, 19 experienced recurrence after 30 days. That's 21% of the patients, and the median episode length of recurrent episodes was 4 minutes. 97% of recurrent episodes were not detected in standard monitoring. If we look at the episode lengths, we see that most episodes are quite short, under an hour, and only 15 episodes had a length greater than 24 hours. We know this length greater than 24 hours for subclinical AF is relevant because in the ASSERT trial, they found that the stroke risk is higher for subclinical AF with a length greater than 24 hours, and that's why we looked at that specifically. Of the patients who developed these episodes lasting greater than 24 hours, eight had these episodes prior to discharge, and three patients had these episodes after discharge. Before discharge, the episodes were detected in standard monitoring, and after discharge, they weren't detected in standard monitoring. So in conclusion, the incidence of new onset AF in the first year after CABG is higher than previously reported. The AF burden is very low, especially later than 30 days, and given the known bleeding risk with oral anticoagulants, the very low burden questions the current guidelines recommending long-term oral anticoagulation. In our opinion, if oral anticoagulation is initiated for new onset AF, the indication should be reassessed within the first 30 days. Most patients shouldn't be receiving anticoagulants, and if they do, there should be a reassessment. A lot of the data shows that even a year after surgery, patients still have anticoagulants that were started early after surgery. It kind of suggests that once it's started, it's not stopped, and that could be a long-term issue in these patients. That's why we want to motivate people to reassess the actual indication for the medication. So that's the CABG-AF study for you.

Well, thank you so much. As mentioned, terribly interesting, very clinically relevant, especially in an outpatient setting where we see patients now after CABG weeks and months and years afterwards, and as you said, often still on anticoagulation. Dr. Marcus, you wrote a terribly interesting editorial on that, and I'm sure you'd be happy to ask some questions, comments.

Those are both quite difficult questions. That's one limitation of our study. Obviously, we didn't test does the loop recorder improve anything for the patient, right? And we didn't test what the length of anticoagulation should be. Those are two questions we can't really answer with the study. But we did collect some pathophysiological background that can be maybe extrapolated, but it will never really be able to answer these questions. That has to be answered with a randomized trial. There is currently a randomized trial that's investigating this issue. It's the PACES trial that's looking at three months of anticoagulation combined with antiplatelet therapy for post-operative AF after CABG, which is currently including patients. So I think we have to wait for that trial to really be able to answer that question. Most data suggests that around 25% of patients that have POAF that's been detected actually receive anticoagulants, and it's pretty stable and similar in different regions of the world from what I've seen from the data. It was similar in our trial. It was around 27% of patients that received anticoagulants. Interestingly, we did not have an effect on or we didn't decide whether patients were anticoagulated or not. That was decided by the treating physicians. But we obviously provided the information of whether they had AF or not. And at the end of the first year, a similar amount of patients still were anticoagulated. So that kind of shows what the current situation is. What I would recommend is patients with a high burden of AF should probably be considered for anticoagulation. And in these patients after 30 days, you should see if they still have a high burden of AF. From the data that we have, most almost all will not have the high burden, and you should probably discontinue the anticoagulation. But obviously, there's no hard data available to answer this question.

I have one question actually before we have to look at the time. Obviously, it's a study on CABG as you said. Can you, I know we can't extrapolate, but what's your thought on real open heart surgery? So not only opening thorax and putting them on a machine, but also incising the left atrium for mitral valve surgery. Would you believe that's a different story? I mean, many mitral valve patients have AF anyway, but if they hadn't had it before the operation and they start afterwards, we'd probably keep them on anticoagulation, wouldn't we?

That's a very good question. If you look at the inclusion and exclusion criteria of our study, we tried to involve this idea that patients are very different even in a specific cohort. So we excluded patients with reduced ejection fraction especially for this reason, and also patients with preoperative AF especially for this reason, because we wanted a clean cohort where we can actually make a comment about how much AF these patients had. And if we look at different types of cardiac surgery, it gets even more important. CABG patients have a lower risk of AF postoperatively compared to patients with valvular surgery. That's what registry data tells us. I think that's an important fact also for the guidelines. So my recommendation would be that this should also be considered in the guidelines when recommending how to treat these patients after surgery. There are some studies that have shown that the stroke risk in POAF after valvular surgery might be higher than that after CABG.

Thanks so much to the two of you. I believe 2025 has been another amazing year for atrial fibrillation research with important studies, surely including DECAF and CABG-AF. The findings are definitely important not only for cardiologists but also for other doctors in internal medicine like neurologists, since all of us see and care for these patients. We're positive that we will see more great data in 2026 from Munich, from San Francisco, and from elsewhere. We would love to see you back then with your new results. Until then, we will finalize our academic year next week with our top 10 of cardiology and lipidology 2025 in German language. Without disclosing the results too early, we will hear on coffee and atrial fibrillation again. So stay tuned, and we wish Merry Christmas and a happy 2026 in Bavaria, in California, and everywhere else. Thank you.